1School of Public Health, The University of Michigan,Ann Arbor, MI 48109–2029, USA. 2Department ofDermatology, Brown University Medical School,Providence, RI 02903, USA. 3Department of MedicalEthics, University of Pennsylvania School of Medicine,Philadelphia, PA 19104–3308, USA.

*Author for correspondence. E-mail: merz@mail:med.upenn.edu

11 FEBRUARY 2005 VOL 307 SCIENCE www.sciencemag.orgPublished by AAAS

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There is growing concern about thepoliticization and social control of science,constraining the conduct, funding,publication, and public use of scientificresearch (1). For example, human cloningand embryonic stem cell creation have beenregulated or banned (2), activists have beenlobbying Congress to remove funding fromcertain government-sponsored research(3–5), and science journal editors have beencompelled to develop policies for publicationof sensitive manuscripts (6, 7).Forbidden knowledge embodies the ideathat there are things that we should not know(8–15). Knowledge may be forbiddenbecause it can only be obtained through unacceptablemeans, such as human experimentsconducted by the Nazis (9, 11); knowledgemay be considered too dangerous, as withweapons of mass destruction or research onsexual practices that undermine social norms(8, 9, 12); and knowledge may be prohibitedby religious, moral, or secular authority,exemplified by human cloning (10, 12).Beyond anecdotal cases, little is knownabout what, and in what ways, science isconstrained. To begin to fill this gap, we performedan interview study to examine howconstraints affect what scientists do. In2002–03, we conducted 10 pilot and 41 indepthsemistructured interviews with a sampleof researchers drawn from prestigiousU.S. academic departments of neuroscience,sociology, molecular and cellular biology,genetics, industrial psychology, drug andalcohol abuse, and computer science. Wechose diverse disciplines to gauge the range,rather than prevalence, of experiences.We asked subjects to consider their practicesand rationales for limiting scientificinquiry or dissemination and to tell us aboutcases in which research in their own disciplinehad been constrained. Respondents reported awide range of sensitive topics, including studiesrelating to human cloning, embryonicstem cells, weapons, race, intelligence, sexualbehaviors, and addiction, as well as concernsabout using humans and animals in research.Nearly half the researchers felt constrainedby explicit, formal controls, such as governmentalregulations and guidelines codified byuniversities, professional societies, or journals.Respondents generally agreed that formalcontrols offered important protections.Less consensus surrounded the necessity,efficiency, or good sense of specific policies.Stem cell research was repeatedly identifiedas an example of an overly restricted area.Many respondents expressed a preference thatscientists—not policy-makers—determinewhich research is too dangerous.We were surprised, however, that respondentsfelt most affected by what we characterizeas “informal constraints.” Researcherssometimes only know that they have encounteredforbidden knowledge when theirresearch breaches an unspoken rule and isidentified as problematic by legislators, newsagencies, activists, editors, or peers. Studiesby Kinsey et al. (16, 17), Milgram (18),Humphreys (19), Herrnstein and Murray (20),and Rind et al. (21) were attacked only afterpublication. Many researchers (42%)described how their own work had been targetedfor censure. One researcher was accusedby activists of “murderous behavior” becausehe was incapable of reporting HIV+ subjectswho admitted to unsafe sex practices in ananonymous survey. A sociologist published anarticle that undermined the central claim of aparticular group, who allegedly then accusedhim of funding improprieties.In other cases, the mere threat of socialsanction deter red particular types ofinquiry. Several researchers said that theirchoices to study yeast or mice instead ofdogs were guided by fears of retributionfrom animal rights groups. As one respondentcommented, “I would like to lunaticproofmy life as much as possible.” Drugand alcohol researchers reported similarfears, stating that they had not pursued studiesthat might provoke moral outrage.Finally, there may be unspoken rulesshared by the community. As one respondentstated, “every microbiologist knowsnot to make a more virulent pathogen.”We failed to detect a coherent ethosregarding production of forbidden knowledge.Respondents at once decried externalregulation and recognized the right of societyto place limits on what and how science isdone. They stated that scientists are “moral”and “responsible,” but acknowledged casesin which scientists were sanctioned for actingoutside the mainstream of their disciplines.They also said that, although informationand “truth” had inherent utility, fulland open publication was not always possible.Whereas most respondents worked hardto avoid controversy, others relished it.In summary, formal and informal constraintshave a palpable effect on what scienceis studied, how studies are performed, howdata are interpreted, and how results are disseminated.Our results suggest that informallimitations are more prevalent and pervasivethan formal constraints. Although formal constraintswill bias science—by affecting whatis studied and how it is studied—these biasesare relatively transparent and amenable topolitical change. Informal constraints, in contrast,may be culturally ingrained and resistantto change, leaving few markers by which toassess their effects. We believe it is importantto observe these constraints, assess theireffects, and openly debate their desirabilityfor science and society.References and Notes1. R.A. Charo, J. Law Med. Ethics32, 307 (2004).2. G.Q. Daley, New Engl. J. Med.349, 211 (2003).3. J. Kaiser, Science300, 403 (2003).4. J. Kaiser, Science302, 758 (2003).5. J. Kaiser, Science302, 966 (2003).6. J. Couzin, Science297, 749 (2002).7. Journal Editors and Authors Group, Science299, 1149(2003).8. C. Cohen, New Engl. J. Med. 296, 1203 (1977).9. D. Smith, Hastings Center Rep. 8 (6), 30 (1978).10. G. Holton, R. S. Morison, Eds., Limits of ScientificInquiry(Norton, New York, 1979).11. D. Nelkin, in Ethical Issues in Social Science Research,T. L. Beauchamp, R. R. Faden, R. J.Wallace, L.Walters,Eds. (Johns Hopkins Univ. Press, Baltimore, MD, 1982),pp. 163–174.12. R. Shattuck, Forbidden Knowledge: From Prometheusto Pornography(Harcourt Brace, New York, 1996).13. D. B. Johnson, Monist79, 197 (1996).14. B. Allen, Monist79, 294 (1996).15. D. B. Johnson, Sci. Eng. Ethics5, 445 (1999).16. A. C. Kinsey et al., Sexual Behavior in the Human Male(Saunders, Philadelphia, 1948).17. A. C. Kinsey et al., Sexual Behavior in the HumanFemale(Saunders, Philadelphia, 1953).18. S. Milgram, Obedience to Authority: An ExperimentalView(Harper Row, New York, 1974).19. L. Humphreys, Tearoom Trade: Impersonal Sex inPublic Places(Aldine, Chicago, 1970).20. R. Herrnstein, C. Murray, The Bell Curve: Intelligenceand Class Structure in American Life (Simon &Schuster, New York, 1996).21. B. Rind et al., Psychol. Bull.124, 22 (1998).22. This study was approved by the University ofPennsylvania Institutional Review Board.We thank allrespondents for their participation; B. Sitko for assistance;and C. Bosk, A. Caplan, J. Drury, C. Lee, and B.Sampat for comments. Supported by the GreenwallFoundation (J.K., C.S.P., J.F.M.) and the Robert WoodJohnson Foundation (J.K.).Supporting Online Materialwww.sciencemag.org/cgi/content/full/307/5711/854/DC110.1126/science.1107576TSS